The present invention relates to the filling of valve bags with particulate material and, more particularly, to a method and apparatus including a novel fill spout for filling valve bags with particulate materials while insuring that a proper valve seal is obtained so that leakage of material through the valve is virtually eliminated.
Particulate materials are commonly packaged in bags that are made from multiple layers of paper and have a "valve" in one upper corner. The valve provides an opening through which the material is dispensed during the bag filling operation.
The valve bag is typically filled by inserting a spout or nozzle into the valve and causing material to flow through the nozzle into the bag. When the bag is full, the flow of material is halted and the nozzle is withdrawn from the valve usually by moving the bag away from the nozzle. The valve is sealed to prevent egress of the material from the bag during shipping and handling.
Various techniques have been used to seal the valve. These techniques depend somewhat on the type of materials being packaged and the type of valve employed. For example, U.S. Pat. No. 3,192,967 to White, Jr. et al discusses a "tuck-in" valve that extends outwardly beyond the side of the bag and is folded inwardly to seal the bag. Also discussed in the White, Jr. et al patent is a commonly used interior or insert sleeve valve that collapses to provide a seal when the valve is filled and the nozzle is removed. White, Jr. et al attempt to obtain a good seal with these types of valves by using a vacuum source to draw air through a conduit in the nozzle as the bag is withdrawn from the nozzle to remove the nozzle from the valve. This action is intended to remove material from the interior of the nozzle and from the valve so that the valve will seal properly. In U.S. Pat. No. 3,083,780 to Swenson also relating to the filling of bags with tuck-in valves or glued interior valves, steps are also taken to remove material from the valve before removal of the bag from the nozzle, but this material removal is effected by blowing the material in the nozzle into the bag prior to disengagement.
U.S. Pat. No. 4,066,108 to Lau shows another valve arrangement which is of the exterior or extended variety but is sealed by heat rather than tucking or folding. Lau attempts to provide contamination of the valve interior by the dispensed material by forming a relatively tight seal around the nozzle when it is inserted in the valve and further by inclining the bag so that the valve opening points upwardly upon removal of the nozzle and prior to sealing.
Quite frequently, a poor seal is obtained because of the presence of material in the valve at the end of the filling process despite previous attempts to minimize this problem. For example, it may be difficult or impossible to blow or suck material out of the filling nozzle by suggested prior art techniques because, with continuous suction or inward directed pressure sufficient to clear the nozzle, other undesirable side effects such as sucking material out of the bag through the nozzle or even damaging the bag may result. Thus, without an effective way to clear the nozzle at the end of each filling operation, particulate material may drop from the nozzle when it is withdrawn from the valve and material may be deposited in the valve. This deposited material then prevents the sides of the valve from properly closing against each other to form a proper seal, and material leakage through the poorly sealed valve may result.
Also, it may require several operations to fill and seal a valve bag by known techniques. For example, a filling operation performed with the bag in one position may be followed by a sealing operation with the bag moved to another position as is described in Lau U.S. Pat. No. 4,066, 108 or in Swenson U.S. Pat. No. 3,083,780. It will be appreciated that such a system for filling and sealing bags, in addition to requiring two operations and the attendant equipment, may be subject to poor sealing since material may enter the valve from the end of the filling nozzle when the bag is moved to the sealing position and the nozzle emerges from the valve. This may be a particular problem in a glued sleeve sealing system such as that shown in the Swenson patent in which the bag is moved through a considerable distance and then the glue on the interior valve is sprayed with water without any prior cleaning of the valve surface.